<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
        function show_confirm() {
            var r = confirm("Press a button!");
            if (r == true) {
                alert("You pressed OK!");
            } else {
                alert("You pressed Cancel!");
            }
        }
    </script>
</head>
<body>
<input type="button" onclick="show_confirm()" value="Show a confirm box"/>
</body>
</html>